Several types of data storage devices, such as flash memory devices, store data in cells of non-volatile media. A physical property of each cell, such as a stored charge, voltage, material phase, electrical resistance, magnetization, or the like, is alterable to encode data. A cell's physical property may be variable across a range, which may be divided into discrete states, so that different states correspond to different data values. Sensing whether the cell's physical property satisfies one or more read thresholds (e.g., voltage thresholds, resistivity thresholds, or the like) within its range determines the cell's state, thus allowing recovery of a stored data value.
The data-encoding physical property of a cell may vary over time due to cell damage, charge leakage, temperature effects, disturbances from nearby cells, or the like. An error may occur if the cell moves from one state into an adjacent state. As storage density increases, feature size shrinks, making the cells more susceptible to such disturbances. Appropriate management of various configuration parameters may reduce error rates by compensating for such disturbances.
Configuration parameters may be managed differently for different blocks of non-volatile storage cells. For example, a first block with a long data retention time may be susceptible to charge leakage that lowers stored voltages, but a second block may be more susceptible to raised voltages, due to disturbances from programming nearby cells. Thus, managing configuration parameters may include lowering the read voltage thresholds between states for the first block, but raising the read voltage thresholds for the second block. Managing configuration parameters separately for each block may account for arbitrary variations between blocks, but may also be resource-intensive.